As a solid-state imaging device (image sensor) using a photo-electric conversion element detecting light and generating a charge, a CMOS (Complementary Metal Oxide Semiconductor) image sensor has been put into practical use. CMOS image sensors have been widely applied as parts of digital cameras, video cameras, monitoring cameras, medical endoscopes, personal computers (PC), mobile phones and another portable terminals (mobile devices), and various other electronic apparatuses.
A CMOS image sensor has photodiodes (photo-electric conversion elements) and floating diffusion (FD) amplifiers having FD layers corresponding to the individual pixels. Readout is performed mainly by the column parallel output method of selecting one row of the pixel array and simultaneously reading out the pixels in the column output direction.
In this regard, in order to improve the characteristics, various methods for realizing a CMOS image sensor having a high image quality with a wide dynamic range have been proposed (see for example PLT 1).
PLT 1 discloses a dynamic range widening technique for dividing the imaging into two or more exposure times different from each other, that is, imaging corresponding to a high illuminance side by a short exposure time and imaging corresponding to a low illuminance by a long exposure time. Further, PLT 1 discloses a dynamic range widening technique which makes the capacities of the floating diffusions FD variable.